Summary:

BACKGROUND:

Some researchers claim that people only lose weight on very low carb diets due to a reduction in calorie intake. Others have argued that very low carb diets offer a “metabolic advantage” allowing people to lose weight without restricting calories. The objective of this study was to evaluate if people who follow very low carb diets lose weight only due to restricting calories.

METHOD:

Twenty-one participants were recruited and were randomly assigned to three separate diets for 12 weeks: a low fat diet (55% carb, 15% protein, and 30% fat) and two different very low carb diets (both had 5% carb, 30% protein, and 65% fat). The low fat (LF) diet and one of the very low carb (LC1) diets provided a total of 1500 calories a day for women and 1800 calories a day for men. The second very low carb diet group was allowed 300 additional calories a day (1800 calories for women and 2100 calories for men). Meals were provided during the study.

RESULTS:

After 12 weeks, all participants lost weight. Both the very low carb groups lost more weight than the low fat group (LC1: -23 lbs, LC2: -20 lbs, and LF: -17 lbs). The difference between the diets was not statistically significant. More body fat was lost than lean body mass (such as muscle) or water on all the diets. All participants lost inches from their waist and hips.

CONCLUSION:

All three diets were effective in reducing weight in adults and the weight lost was primarily body fat. Even participants consuming higher calories on the very low carb diet were able to lose more weight compared to the lower calorie, low fat diet. Several risk factors for heart disease improved on all diets. The authors concluded that very low carb diets do not reduce weight only by restricting calories.